Harvested water that has been properly filtered and stored can be recycled into a number of uses. Regulations in some states and municipalities restrict the uses of harvested water and should be carefully checked for compliance before a system is designed.


While it seems almost a shame to use carefully collected and stored rainwater or greywater to flush toilets, this important use of harvested waters can make a significant reduction in the use of potable water purchased from your local utility.

Toilets and urinals consume as much as 40% – 60% of water purchased for a typical office building. By supplementing or eliminating this wasteful use of potable water, “green” buildings not only reduce their municipal water bills, but also contribute to conserving a valuable, limited resource in our environment. The filtering and sterilizing steps included in the Water Harvesting Solutions systems turn greywater into clear, clean water, making it highly suitable for toilet flushing.

You can get a rough estimate of how much water your building will require for toilet flushing using our water harvesting calculator


Harvested rainwater is often used to irrigate landscaping. What could be more natural than carefully saving excess rainwater to water plants and lawns around a facility? This use of harvested rainwater is particularly effective in areas that experience rain events on a periodic basis throughout the irrigation season. These systems are designed to store enough harvested rain to bridge rain events by 2-3 weeks.

In areas where rain events are seasonal and long gaps are typical during a “dry season” greywater may be a better water source for supply. The most reliable sources of greywater are available in buidlings with residents using showers and sinks. For more information on greywater as a source, click here.

A properly designed system will apply only as much harvested water as needed by each irrigation zone. That amount is determined based on the evapotransporation or “E.T.” of the landscaping, which is calculated using he amount of rainfall, temperature, variations, humidity, wind, soil type and topography of the property. For information on E.T. irrigation controllers, visit

To meet the needs of our clients for complete sustainable irrigation solutions, Wahaso has partnered with Landtech Design for the design of irrigation systems to effectively distribute harvested water from our systems. Established in 1994, Landtech provides solutions on challenging irrigation projects with a thorough and seamless sequence of involvements (planning, design, implementation). Landtech’s most differentiating factors are: expertise in low-volume & drip-irrigation, and the desire & willingness to discuss with clients the options available for ‘control’ of the project once it’s in the hands of the end-user (controller’s hardware, software, communication methods, hand-held capabilities, etc.)

Systems designed and installed by Water Harvesting Solutions can meet the purity standards for water quality of any community where properly prepared greywater and rainwater are legally permitted for landscape irrigation.


Depending on the building’s location and function, other uses for the harvested water may be considered. During the Consulting Phase, Wahaso can help assess the most effective approach for managing the supply and demand of harvested water for any project.

Cooling Towers

Cooling towers can be large consumers of water – 40% or more for a typical office building – and are an excellent use of harvested water. A typical commercial building with an evaporative cooling system can used 2-3 million gallons of water in a season to “make-up” water lost through evaporation and the “blow-down” cleaning cycle. Read more about water harvesting and cooling towers.

Boiler Make-Up

Boilers in a commercial building can consume thousands of gallons of water per day. Harvested water can serve as “make-up” for water lost in the heating cycle.

Fire Suppression Systems

Commercial buildings with can easily have 100,000 gallons or more of stored harvested water that can be readily available for an automatic fire suppression system or as an additional water source for pumping trucks in the event of a property fire. This stored bulk water could be especially important in communities with inadequate water pressure or water main capacity.

Industrial Applications

Buildings for water-intensive industrial use can also benefit from water harvesting. These buildings frequently have large roof and parking surface areas with a significant potential for capturing and harvesting rainwater. Even if the harvested water is a relatively small percentage of total use, it application can be part of an overall effort to reduce the building’s impact on the environment.

Clothes Washing

Harvested water may be useful in buildings doing large quantities of laundry – such as a dormitory or correctional facility.